Editing Wheat (section)

== Description ==

[[File:Triticum aestivum - Köhler–s Medizinal-Pflanzen-274.jpg|thumb|A: Plant; B ripe ear of corn; 1 [[spikelet]] before flowering; 2 the same, flowering and spread, enlarged; 3 flowers with [[glume]]s; 4 [[stamen]]s 5 [[pollen]]; 6 and 7 ovaries with juice scales; 8 and 9 parts of the scar; 10 fruit husks; 11, 12, 13 seeds, natural size and enlarged; 14 the same cut up, enlarged.]]

Wheat is a stout grass of medium to tall height. Its stem is jointed and usually hollow, forming a straw. There can be many stems on one plant. It has long narrow leaves, their bases sheathing the stem, one above each joint. At the top of the stem is the flower head, containing some 20 to 100 flowers. Each flower contains both male and female parts.<ref name="Brittanica"/> The flowers are [[wind-pollinated]], with over 99% of pollination events being [[self-pollination]]s and the rest [[cross-pollination]]s.<ref>{{Cite journal |last1=Yang |first1=Hong |last2=Li |first2=Yongpeng |last3=Li |first3=Dongxiao |last4=Liu |first4=Liantao |last5=Qiao |first5=Yunzhou |last6=Sun |first6=Hongyong |last7=Liu |first7=Wenwen |last8=Qiao |first8=Wenjun |last9=Ma |first9=Yuzhao |last10=Liu |first10=Mengyu |last11=Li |first11=Cundong |last12=Dong |first12=Baodi |display-authors=6 |date=9 June 2022 |title=Wheat Escapes Low Light Stress by Altering Pollination Types |journal=Frontiers in Plant Science |volume=13 |page=924565 |doi=10.3389/fpls.2022.924565 |doi-access=free |pmid=35755640|pmc=9218482 }}</ref> The flower is housed in a pair of small leaflike [[glume]]s. The two (male) [[stamen]]s and (female) [[Stigma (botany)|stigma]]s protrude outside the glumes. The flowers are grouped into [[spikelet]]s, each with between two and six flowers. Each fertilised [[carpel]] develops into a wheat grain or berry; botanically a [[caryopsis]] fruit, it is often called a seed. The grains ripen to a golden yellow; a head of grain is called an ear.<ref name="Brittanica">{{cite encyclopedia |title=wheat (plant) |url=http://www.britannica.com/EBchecked/topic/641558/wheat |encyclopedia=britannica.com |accessdate=23 December 2023}}</ref>

Leaves emerge from the shoot apical [[meristem]] in a telescoping fashion until the transition to reproduction i.e. flowering.<ref>{{cite web |url=https://www.ipipotash.org/udocs/ipi-bulletin-17-cereals.pdf |title=Fertilising for High Yield and Quality – Cereals}}</ref> The last leaf produced by a wheat plant is known as the flag leaf. It is denser and has a higher [[photosynthesis|photosynthetic]] rate than other leaves, to supply [[carbohydrate]] to the developing ear. In temperate countries the flag leaf, along with the second and third highest leaf on the plant, supply the majority of carbohydrate in the grain and their condition is paramount to yield formation.<ref name="Pajević-1999">{{cite journal |jstor=23786279 |title=Photosynthesis of Flag and Second Wheat Leaves During Senescence |journal=Cereal Research Communications |volume=27 |issue=1/2 |pages=155–162 |last1= Pajević |first1=Slobodanka |last2=Krstić |first2= Borivoj |last3=Stanković|first3=Živko |last4=Plesničar |first4=Marijana |last5=Denčić |first5=Srbislav |year=1999 |doi=10.1007/BF03543932}}</ref><ref name="Araus-1986">{{Cite book |doi=10.1007/978-94-009-4384-1_18 |chapter=Photosynthesis, Nitrogen Levels, and Dry Matter Accumulation in Flag Wheat Leaves During Grain Filling |title=Biological Control of Photosynthesis |pages=199–207 |year=1986 |last1=Araus |first1=J. L. |last2=Tapia |first2=L. |last3=Azcon-Bieto |first3=J. |last4=Caballero |first4=A. |isbn=978-94-010-8449-9}}</ref> Wheat is unusual among plants in having more [[stomata]] on the upper ([[adaxial]]) side of the leaf, than on the under ([[abaxial]]) side.<ref>{{Cite journal |jstor=23783891|title=Stomatal Size, Frequency and Distribution in ''Triticum Aestivum'', ''Secale Cereale'' and Their Amphiploids|journal=Cereal Research Communications |volume=23|issue=1/2|pages=103–108 |last1=Singh |first1=Sarvjeet |last2=Sethi |first2=G.S. |year=1995}}</ref> It has been theorised that this might be an effect of it having been [[domestication|domesticated]] and cultivated longer than any other plant.<ref>{{Cite journal |doi=10.1093/jxb/ert147 |pmid=23918960 |title=Shifts in stomatal traits following the domestication of plant species |journal=[[Journal of Experimental Botany]] |volume=64 |issue=11 |pages=3137–3146 |year=2013 |last1=Milla |first1=Rubén |last2=De Diego-Vico |first2=Natalia |last3=Martín-Robles |first3=Nieves |doi-access=free}}</ref> [[Winter wheat]] generally produces up to 15 leaves per shoot and spring wheat up to 9<ref name="AHDB">{{cite web |url=https://cereals.ahdb.org.uk/media/185687/g66-wheat-growth-guide.pdf |title=Wheat Growth Guide |publisher=[[Agriculture and Horticulture Development Board]]}}</ref> and winter crops may have up to 35 [[tiller (botany)|tiller]]s (shoots) per plant (depending on cultivar).<ref name="AHDB"/>

Wheat [[root]]s are among the deepest of arable crops, extending as far down as {{convert|2|m}}.<ref>{{cite book |url=https://books.google.com/books?id=XedeDwAAQBAJ&q=wheat+roots+2+metres&pg=PA39 |title=Wheat Crop Management |isbn=9789387741287 |last1=Das |first1=N. R. |date=1 October 2008 |publisher=Scientific Publishers }}</ref> While the roots of a wheat plant are growing, the plant also accumulates an energy store in its stem, in the form of [[fructans]],<ref>{{Cite journal |pmc=1075255 |year=1986 |last1=Hogan |first1=M. E. |title=Labeling of Fructans in Winter Wheat Stems |journal=[[Plant Physiology]] |volume=80 |issue=4 |pages=1048–1050 |last2=Hendrix |first2=J. E. |pmid=16664718 |doi=10.1104/pp.80.4.1048}}</ref> which helps the plant to yield under drought and disease pressure,<ref>{{cite journal |pmc=4531436 |year=2015 |last1=Zhang |first1=J. |title=Wheat genotypic variation in dynamic fluxes of WSC components in different stem segments under drought during grain filling |journal=[[Frontiers in Plant Science]] |volume=6 |pages=624 |last2=Chen |first2=W. |last3=Dell |first3=B. |last4=Vergauwen |first4=R. |last5=Zhang |first5=X. |last6=Mayer |first6=J. E. |last7=Van Den Ende |first7=W. |pmid=26322065 |doi=10.3389/fpls.2015.00624 |doi-access=free}}</ref> but it has been observed that there is a trade-off between root growth and stem non-structural carbohydrate reserves. Root growth is likely to be prioritised in drought-adapted crops, while stem non-structural carbohydrate is prioritised in varieties developed for countries where disease is a bigger issue.<ref>{{cite journal |title=Partitioning of assimilates to deeper roots is associated with cooler canopies and increased yield under drought in wheat |journal=[[Functional Plant Biology]] |volume=37 |issue=2 |pages=147 |citeseerx=10.1.1.535.6514 |doi=10.1071/FP09121|year=2010 |last1=Lopes |first1=Marta S. |last2=Reynolds |first2=Matthew P. }}</ref>

Depending on variety, wheat may be [[Awn (botany)|awned]] or not awned. Producing awns incurs a cost in grain number,<ref>{{cite journal |last1=Rebetzke |first1=G. J. |last2=Bonnett |first2=D. G. |last3=Reynolds |first3=M. P. |title=Awns reduce grain number to increase grain size and harvestable yield in irrigated and rainfed spring wheat |journal=[[Journal of Experimental Botany]] |volume=67 |issue=9 |pages=2573–2586 |year=2016 |doi=10.1093/jxb/erw081 |pmid=26976817 |pmc=4861010}}</ref> but wheat awns photosynthesise more efficiently than their leaves with regards to water usage,<ref>{{cite journal |last1=Duwayri |first1=Mahmud  |title=Effect of flag leaf and awn removal on grain yield and yield components of wheat grown under dryland conditions |journal=Field Crops Research |year=1984 |volume=8 |pages=307–313 |doi=10.1016/0378-4290(84)90077-7 |bibcode=1984FCrRe...8..307D }}</ref> so awns are much more frequent in varieties of wheat grown in hot drought-prone countries than those generally seen in temperate countries. For this reason, awned varieties could become more widely grown due to [[climate change]]. In Europe, however, a decline in [[climate resilience]] of wheat has been observed.<ref>{{cite journal |doi=10.1073/pnas.1804387115 |pmid=30584094 |pmc=6320549 |title=Decline in climate resilience of European wheat |journal=Proceedings of the National Academy of Sciences |volume=116 |issue=1 |pages=123–128 |year=2019 |last1=Kahiluoto |first1=Helena |last2=Kaseva |first2=Janne |last3=Balek |first3=Jan |last4=Olesen |first4=Jørgen E. |last5=Ruiz-Ramos |first5=Margarita |last6=Gobin |first6=Anne |last7=Kersebaum |first7=Kurt Christian |last8=Takáč |first8=Jozef|last9=Ruget |first9=Francoise |last10=Ferrise |first10=Roberto |last11=Bezak |first11=Pavol |last12=Capellades |first12=Gemma |last13=Dibari |first13=Camilla|last14=Mäkinen |first14=Hanna |last15=Nendel |first15=Claas |last16=Ventrella |first16=Domenico |last17=Rodríguez |first17=Alfredo |last18=Bindi |first18=Marco |last19=Trnka |first19=Mirek |display-authors=5 |bibcode=2019PNAS..116..123K |doi-access=free}}</ref>